Remove the proxy callback tracker.

ppapi/proxy/dispatcher.h

Index: ppapi/proxy/dispatcher.h
diff --git a/ppapi/proxy/dispatcher.h b/ppapi/proxy/dispatcher.h
index a48cff7e7a29750a95f91e4b4d0624017326d579..aca1f784755748e2124d87a9731c8d5bffafb17e 100644
--- a/ppapi/proxy/dispatcher.h
+++ b/ppapi/proxy/dispatcher.h
@@ -14,7 +14,6 @@
 #include "ipc/ipc_channel_proxy.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_module.h"
-#include "ppapi/proxy/callback_tracker.h"
 #include "ppapi/proxy/proxy_channel.h"
 #include "ppapi/proxy/interface_id.h"
 #include "ppapi/proxy/interface_list.h"
@@ -83,10 +82,6 @@ class PPAPI_PROXY_EXPORT Dispatcher : public ProxyChannel {
   // IPC::Channel::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& msg);
 
-  CallbackTracker& callback_tracker() {
-    return callback_tracker_;
-  }
-
   GetInterfaceFunc local_get_interface() const { return local_get_interface_; }
 
  protected:
@@ -116,8 +111,6 @@ class PPAPI_PROXY_EXPORT Dispatcher : public ProxyChannel {
 
   GetInterfaceFunc local_get_interface_;
 
-  CallbackTracker callback_tracker_;
-
   scoped_ptr<VarSerializationRules> serialization_rules_;
 
   DISALLOW_COPY_AND_ASSIGN(Dispatcher);